Discharge lamp



Oct. 13, 1936. c. P. BRocKwAY DISCHARGE LAMP Filed Oct. 28, 1932 2Sheets-Sheet 1 llll I I @NNUQNVV FMMWMMMIE a 0457 INVENTOR.

CARL l BRockwny BY WWW A TTORNEY Oct. 13, 1936. c. P. BROCKWAY 2,056,953

DISCHARGE LAMP 7 Filed 001?. 28, 1932 2 Sheets-Sheet 2 'jalylilINVENTOR. CARL F BROCkWAY ATTORNEY Patented Oct. 13, 1936 OFFICEDISCHARGE LADIP Carl P. Brockway, Paramus, N. J., minor to NationalTelevision Corporation, Wilmington, Del., a corporation of DelawareApplication October 28, 1932, sem No. 639,973

6 Claims. (01.176-122) This invention relates to discharge lamps andparticularly to that type of discharge lamp for producing modulatedlight.

One of the objects of the invention is to provide a discharge lamp inwhich a continuous ionization of the gas is maintained during theoperation of the lamp. j

Another object of the invention is to provide a discharge lamp in whichthe discharge is prevented from being extinguished due to heavymodulations in the operating current.

Another object of the invention is to provide a discharge lamp in whichthe discharge is shifted from one path to another by the modulatingcurrent.

Still another object of the invention is to provide a discharge lampwith a plurality of elements so arranged that the useful discharge willoccur between two of the elements while a nonuseful discharge will occurbetween another two.

Other objects of the invention and objects relating particularly to themethod of assembling and constructing the various parts will be apparentas the description proceeds.

Several embodiments of the invention have been illustrated in theaccompanying drawings, in which: I

Fig. 1 is a sectional side elevation view of a lamp illustrating oneform of the invention which 30 may be preferred;

Fig. 2 is a front elevational view of the lamp of Fig. 1;

Fig. 3 is a fragmentary sectional view of the cathode of Figs. 1 and 2;

Fig. 4 is a sectional side elevational view of vention;

Fig. 5 is a front elevational view of the lamp of Fig. 4;

Fig. 6 is a sectional side elevational View of a modified form of thelamp of Fig. 1;

Fig. 7 is an enlarged sectional view of a portion of the cathode of Fig.6;

Fig. 8 is a front elevational view of the lamp shown in Fig. 6;

Fig. 9 is a circuit diagram showing another manner of connecting thelamp of Figs. 6, 7, and 8; and 4 Fig. 10 is a side elevational view ofanother form of lamp embodying the invention.

Referring now more specifically to the drawings, the invention is shownin Fig. 1 as comprising an envelope in of glass or other suitabletransparent material having a neck H which is fused to the usualinturned press ii for supa lamp illustrating a different form of theinporting the various elements of the device. A pair of solid cathodesl3 and I4 are mounted in approximately the center of the envelope andspaced from each other. These cathodes may be made of any suitablerefractory metal such 5 as tungsten, molybdenum, tantalum, iron, or evensofter metals, such as nickel and copper. As indicated, they are flatplates somewhat oval in shape and arranged parallel to each otheralthough electrically separated. Any suitable 10 means may be used tomount the cathodes as by means of the support rod l5 which may be weldedto the cathode l3 at the bottom thereof, and the support rod l6 whichmay be welded to the lower end of the cathode M. The sup- 15 port rodsl5 and It may be sealed in the press l2 in a well known manner andlead-in wires I1 and I8 may be connected respectively to them for makingthe outside connection for the lamp.

The cathode l3 may have a hole 19 extending therethrough, positioned onthe central line of the cathode but somewhat above the exact centerthereof. In like manner the cathode l4 may have a hole 20 positioned onthe central axis but below the exact center thereof so as to be out ofalignment with the hole l9 and the cathode l3.

An anode 2| having a shape similar to the cathode l3 although lighter inweight and composed, if desired, of a similar metal, may be 30 mountedon a support rod 22 as by welding, and the support rod may be sealed inthe press I 2 spaced from the support rod l5 as indicated. A lead-inwire 23 may be attached to the support rod 22 for making the externalconnection to 5 the anode 2|. At a point aligned with the hole IS in thecathode I3 I provide a somewhat smaller hole in the anode so that thehole IS in the cathode l3 may be viewed through the hole in the anode.

A second anode 25 may be positioned in like manner spaced slightly fromthe cathode l4. This anode is also about the same size and shape as thecathode l4, although it may be formed of somewhat lighter material, andis mounted upon 45 a support rod 26 which is sealed in the press I2. Alead-in wire 21 may be connected to the support rod 26 for making theexternal connection. The anode 25 may also be provided with a hole 28which is in alignment with the hole 50 20 in the cathode it.

Both cathodes l3 and I4, and the anodes too. if desired, may be coatedwith a material 29, which is relatively low in electron emission so asto eliminate or cut down as far as possible the 56 electron emissionfrom the surface of the oathode, except in the interior of the holes l9and 20 where the material is omitted. This material may be any suitableinsulating material, or if desired, the cathodes may be coated with lampblack, or otherwise carbonized, carbon having apparently the eiiect ofcutting down electron emission to a minimum.

With the elements mounted as described above, the envelope may beconnected to a vacuum pump and an oven placed over it to raise thetemperature thereof together with the enclosed elements so as to driveout all occluded gases from the elements and envelope. When the partshave been thoroughly freed from gases in a manner well known in the art,a suitable ionizable gas may be admitted to the envelope at a relativelylow pressure so as to permit a discharge forming between the anodes andcathodes when a suitable potential is applied between them. This gas maybe one of the monatomic gases, such as neon, argon, helium, krypton, andxenon, or mixtures of such gases, and under certain conditions where itis desired to increase conductivity or to produce color efiects, metalvapors may be added, such as the vapors of mercury, caesium, sodium,rubidium, and the like. The pressure of the gas should be under 15 mm.of mercury and probably best results are obtained with pressure in theneighborhood of 5 mm.

If one of the cathodes and its adjacent anode are connected to a sourceof modulated current at a suitable voltage, it will be evident that adischarge will torm between the cathode and anode and will concentratein the hole provided in the cathode which will then act as a crater, andthis discharge can be observed through the hole in the anode which maythen act as a frame to limit the size of the light source to apredetermined dimension.

I may, however, prefer to connect the lamp in a diiTerent manner asclearly indicated in Fig. 1. Here the two cathode leads I! and i8 areconnected by means of wires 30 and 3| respectively to the terminals 32and 33 of an incoming source of modulated current such as that producedby a television signal or a sound program picked up by a microphone. Awire 34 is connected to both wires 23 and 21 which form the two anodeleads and is connected through a battery 35 to a neutral point of themodulated circuit by means of a resistance 36 which is placed across thewires 30 and 3| and to the center of which the negative side of thebattery 35 is connected. In a typical set-up a battery voltage of 200volts is employed to initiate the discharge between the cathode andanode with a current ranging from 60 to milliamperes.

As the incoming current fluctuates due to the modulations received, thepolarity of the oathodes I3 and I4 will change, one always being morenegative than the other depending on the strength of the modulation. Asthe two anodes 2| and 25 are connected together, their potential will bethe same and hence a discharge will form between one of the anodes andwhichever cathode has a more negative potential. This discharge iscaused by the battery 35 which furnishes a constant source of potentialand hence there will be a discharge somewhere in the lamp at all times.However, as the cathode l3, for instance, varies its potential from alow negative towards the positive side, the discharge between the anode2| and cathode |3 will fall ofi while that between the anode 2-5 and thecathode |4 will increase. Hence, while there will always lated lightalthough both are adaptable for use and may be used, if desired.

In Figs. 4 and 5 another modification of the invention is illustrated.Here an envelope I0 is provided with an inturned press |2 in which aresealed three support rods 42, 43, and 44. Upon the support rod 42 Iposition a cathode 45 which is formed of a solid plate of suitable metalhaving an extended portion 45 on one side and a hole or crater 41 on theother side extending into the portion 46. This cathode may be coatedsimilarly to those described above with a coating 48 of carbon or othersuitable material to cut down emission except in the crater 41. Thecathode 45 and support rod 42 are so positioned that they occupy a planespaced somewhat from the center of the lamp.

In approximately the center of the lamp I position a.small anode 49 uponthe support rod 43. This anode may be semi-circular in shape, ifdesired, and may be formed of the same metal as the cathode 45. Ashallow crater 50 is provided in the anode 49 in alignment with thecrater 41 of the cathode 45, and the whole anode together with thesupport rod may be coated with the coating material.

A second and larger anode 5| having a shape similar to the cathode 45may be positioned spaced slightly on the other side of the anode 49 andan opening 52 may be provided in the anode just above the upper edge ofthe anode 49. Leadin wires 53 and 54 may be connected respectively tosupport rods 42 and 43 and a battery 55 or other source of constantpotential may be connected across these two wires with the positive sideof the battery connected to the anode 49 and the negative side to thecathode 45. A leadin wire 56 may also be connected to the support rod 44and anode 5| and may be connected to the terminal 51 for the incomingmodulated current while the other terminal 58 of the incoming circuitmay be connected by means of a wire 59 to the negative side of thebattery 55.

With this construction as indicated in Fig. 4, a direct currentdischarge will flow between the cathode 45 and the anode 49. Thisdischarge will be concentrated in the crater 41 of the cathode and willnot be visible from the front or righthand side of Fig. 4 as it will beobscured by the anode 49. When the anode 5|, however, becomes highlypositively charged due to the modulating current, the potential of whichshould be greater than that of the battery, the discharge will leave theanode 49 and pass over the top thereof to the anode 5| so that it may beclearly viewed through the hole 52 in the anode. There will always be adischarge in the lamp and hence there will be no necessity of buildingup a high starting potential for the modulated current as the dischargewill jump to the anode 5| immediately the potential of the anode ishigher than that of the anode 49 and instantaneous modulation of thelight as viewed'through the hole 52 in the anode 5|, will, therefore, beevident.

I up the lamp of Fig. 6.

A modified form of the construction of Figs. 1 to 3, has beenillustrated in Figs. 6, 7 and 8. Here an envelope I0, provided with theusual press I2, supports a single large solid'cathode 62 and a pair ofanodes 63 and 64 spaced one on each side of the cathode.

The cathode may be formed of any of the metals mentioned above but ispreferably somewhat thicker than either of the cathodes of Fig. 1 andmay be supported on two support rods 66 which are sealed at the centerof the press I 2 and which pass upwardly, one on each side of thecathode. The cathode 62 has a crater 66 in one side thereof positionedabove the center of the cathode while a crater 61 in the other side ofthe cathode is positioned below the center, these craters taking theplace of the two craters l9 and 20 in the cathodes I3 and ll of Fig. 1.The cathode 62 may be covered with a coating 68 of the material low inelectron emissivity which has already been described. The anode 63 maybe provided with an opening 69 in alignment with the crater 66, whilethe anode 66 has an opening 10 in alignment with the crater 61. Theanodes 63 and 64 may be mounted respectively upon support rods H and 12sealed in the press. A lead-in wire 18 may be connected to one of thecathode support rods 65 while lead-in wires 14 and 15 may be connectedrespectively to the support rods H and 12. The lamp may be provided withthe gases as described above.

One way of connecting up the lamp just described is indicated in Fig. 6where a battery 16 has its negative end connected by means of the wire11 to the lead-in wire 13 for the cathode. while the positive side ofthe battery is connected by means of a wire 18 to the mid-point 19 of aresistance 80 connected across the two leads 14 and 15 which may beconnected respectively to the terminals 8| and 82 of the incomingmodulated current circuit.

The lamp functions similarly to that shown in Fig. 1 although oppositethereto. The cathode 62 is given a negative potential by the batterywhile the two anodes are connected to the modulatlng circuit so thatthey vary in potential in accordance with the modulations received.Whichever anode is, therefore, the more positive at the moment willreceive the discharge caused by the battery. Hence there will always bea discharge in the lamp but it will flicker between the crater 66 andanode 63 and the crater 61 and anode 64. The intense discharge appearingin either of the craters 66 and 61 may be viewed in front of theirrespective anodes through the holes 69 and 10 respectively.

In Fig. 9 is shown another means of connecting Here the cathode 62 isconnected by means of a wire 83 to an input terminal 84 of the incomingmodulated circuit, while the anode 63 is connected by means of a wire 85to the other terminal 86 of the incoming circuit. The other anode 64 isconnected by means of a wire 81 to the positive side of a battery 88while the negative side of the battery is connected by means of the wire89 to the wire 83 connected to the cathode. Thus a constant dischargetakes place between the cathode 62 and the anode 64 which tends tomaintain an ionized condition of the gas within the envelope and permitsthe ready formation of discharge between the oathode and anode 63 andmaintains it in spite of heavy modulation with long dark periods.

and 9| are connected together by a relatively long tube 92, the tubebeing fused to the glass bulbs at the tip ends thereof so as to form agas-tight duct between them. The bulb 90 may be'provided with a press 93in which is sealed a support wire 94, and an anode 95 consisting of adisc of suitable metal may be secured as by welding to the end of therod 94. nected to the support rod. 96 and may have its other endattached to the terminal 91 of the incoming modulated current circuit.

The bulb 9| may contain a pair of electrodes 98 and 99 mounted in aspaced position upon support wires I00 and IM respectively. The supportrods are sealed in the press I02 which is fused to the envelope asindicated. The electrodes 98 and 99 may be formed of any suitable metalas mentioned-above and may be circular in form with the edges thereofterminating not far from the opening of the tube 92. A lead-in wire I03may be connected to the support rod I00 and have its other end connectedto the terminal I04 forming the other terminal of the incoming modulatedcurrent circuit. Also a lead-in wire I05 may be connected to the supportrod IM and may be connected to the positive side of a, battery I06 whosenegative side is connected by means of the wire I01 to the wire I03, or,in other words, to the electrode 98. This puts a constant potentialbetween the electrodes 98 and 99 with the result that a constantdischarge will form in the bulb 9|. The negative side of the modulatedcircuit is connected by the wire I03 to the electrode 98 which thereforeforms the cathode for the anode 95 and a modulated discharge will formin the tube 92. Inasmuch as the discharge between the plates 98 and 99is continuous and constant, there will always be ionization in the bulb9 I and hence the discharge can readily start between the electrode 98and the anode 95, thus creating a practically instantaneous response tomodulated input currents.

From the above description it will be seen that I have provided a lampfor use with modulated current in which the ionization in the lamp ismaintained constant so that the discharge can start at relatively lowvoltages and is prevented from being extinguished due to long darkperiods in the modulated circuit and current. The lamp lends itselfparticularly to use with television apparatus in which the modulationsare extremely rapid or may also be used in connection with sound-on-filmapparatus or in any other instance where modulated light is necessary ordesirable.

Many modifications of the invention may be resorted to without departingfrom the spirit thereof, and I do not, therefore, desire to limit myselfto what has been shown and described except as such limitations occur inthe appended claims.

What I desire to secure by Letters Patent and claim is: I k

1. In combination, a discharge lamp comprising a pair of electrodes,means to connect a modulated circuit to said electrodes, means to.create a neutral point between said electrodes, a third electrode withinsaid lamp, a circuit connection between the neutral point and said thirdelectrode and means for impressing a constant potential on said circuitconnection, said electrodes being so arranged that the intense dischargebetween said third electrode and one only of the other electrodes isobservable from a given position.

2. In an apparatus of the class described, a

A lead-in wire 96 may be con- .pair of spaced electrodes, an ionizablegas sur rounding said electrodes, means to connect a source of modulatedcurrent across said electrodes, means to locate approximately theelectrical center between said electrodes, a third electrode spacedbetween said other two electrodes, a circuit connection between saidthird electrode and electrical center, and means to impress a constantpotential upon said circuit connection.

3. A discharge lamp comprising apair oi. closely spaced cathodeselectrically separated from each other, an anode spaced from onecathode, an anode spaced from the other cathode, and an ionizable gassurrounding said cathodes and anodes, said anodes and cathodes being soarranged that the intense discharge between one only of said cathodesand one only of said anodes is visible from a given position.

4. A discharge lamp comprising a pair of flat cathodes with spaced andadjacent faces, a crater in each of said cathodes, said craters beingout of alignment, an anode positioned adjacent one of said cathodes, ananode positioned adjacent the other of said cathodes, and an ionizablegas sursaid anodes having openings therein arranged in alignment withthe craters oi the adjacent cathodes, and an ionizable gas surroundingsaid anodes and cathodes, said anodes being external to said cathodes.

6. A discharge lamp comprising a pair of flat cathodes with spaced andadjacent faces, a crater in each of said cathodes, said craters beingout oi alignment, a coating of material having a low electron emissionon each of said cathodes with the exception of the craters thereof, ananode positioned adjacent one of said cathodes. an

anode positioned adjacent the other of said cathodes, and an ionizablegas surrounding said anodes and cathodes, said anodes being external tosaid cathodes.

' CARL P. BROCKWAY.

